Adrenaline Group

Tyrosine is synthesized from phenylalanine in mammals in quantity (Figure 8.3), while a tiny amount of tyrosine is converted to DOPA (dihydroxyphenylalanine) (Figure 8.7). The second hydroxy 1 is inserted without a shift of hydrogen, unlike the formation of tyrosine (Figure 8.3). DOPA is decarboxylated to dopamine, which in turn gives noradrenaline (norepinephrine), an important neurotransmitter in the autonomic nervous system, and noradrenaline is methylated to adrenaline, a hormone from the adrenal glands of mammals (Figure 8.8). Both dopamine and noradrenaline are found in the venom of wasps and the honeybee, adrenaline is a minor component of wasp venom. There is about 1 mg of dopamine per g of bee venom. These substances appear to be present in the nervous systems of insects and their relatives too. Dopamine, or something like it, stimulates production of pheromone in female ticks after they have taken a blood meal.